include/net/erspan.h - pub/scm/linux/kernel/git/dgc/linux-xfs - Git at Google

 #ifndef __LINUX_ERSPAN_H
 #define __LINUX_ERSPAN_H

 /*
  * GRE header for ERSPAN type I encapsulation (4 octets [34:37])
  *      0                   1                   2                   3
  *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *     |0|0|0|0|0|00000|000000000|00000|    Protocol Type for ERSPAN   |
  *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *
  *  The Type I ERSPAN frame format is based on the barebones IP + GRE
  *  encapsulation (as described above) on top of the raw mirrored frame.
  *  There is no extra ERSPAN header.
  *
  *
  * GRE header for ERSPAN type II and II encapsulation (8 octets [34:41])
  *       0                   1                   2                   3
  *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *     |0|0|0|1|0|00000|000000000|00000|    Protocol Type for ERSPAN   |
  *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *     |      Sequence Number (increments per packet per session)      |
  *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *
  *  Note that in the above GRE header [RFC1701] out of the C, R, K, S,
  *  s, Recur, Flags, Version fields only S (bit 03) is set to 1. The
  *  other fields are set to zero, so only a sequence number follows.
  *
  *  ERSPAN Version 1 (Type II) header (8 octets [42:49])
  *  0                   1                   2                   3
  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |  Ver  |          VLAN         | COS | En|T|    Session ID     |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |      Reserved         |                  Index                |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *
  *
  *  ERSPAN Version 2 (Type III) header (12 octets [42:49])
  *  0                   1                   2                   3
  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |  Ver  |          VLAN         | COS |BSO|T|     Session ID    |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |                          Timestamp                            |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |             SGT               |P|    FT   |   Hw ID   |D|Gra|O|
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *
  *      Platform Specific SubHeader (8 octets, optional)
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |  Platf ID |               Platform Specific Info              |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  * |                  Platform Specific Info                       |
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  *
  * GRE proto ERSPAN type I/II = 0x88BE, type III = 0x22EB
  */

 #include <linux/ip.h>
 #include <linux/ipv6.h>
 #include <linux/skbuff.h>
 #include <uapi/linux/erspan.h>

 #define ERSPAN_VERSION	0x1	/* ERSPAN type II */
 #define VER_MASK	0xf000
 #define VLAN_MASK	0x0fff
 #define COS_MASK	0xe000
 #define EN_MASK		0x1800
 #define T_MASK		0x0400
 #define ID_MASK		0x03ff
 #define INDEX_MASK	0xfffff

 #define ERSPAN_VERSION2	0x2	/* ERSPAN type III*/
 #define BSO_MASK	EN_MASK
 #define SGT_MASK	0xffff0000
 #define P_MASK		0x8000
 #define FT_MASK		0x7c00
 #define HWID_MASK	0x03f0
 #define DIR_MASK	0x0008
 #define GRA_MASK	0x0006
 #define O_MASK		0x0001

 #define HWID_OFFSET    4
 #define DIR_OFFSET     3

 enum erspan_encap_type {
 	ERSPAN_ENCAP_NOVLAN = 0x0,	/* originally without VLAN tag */
 	ERSPAN_ENCAP_ISL = 0x1,		/* originally ISL encapsulated */
 	ERSPAN_ENCAP_8021Q = 0x2,	/* originally 802.1Q encapsulated */
 	ERSPAN_ENCAP_INFRAME = 0x3,	/* VLAN tag perserved in frame */
 };

 #define ERSPAN_V1_MDSIZE	4
 #define ERSPAN_V2_MDSIZE	8

 struct erspan_base_hdr {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	__u8	vlan_upper:4,
 		ver:4;
 	__u8	vlan:8;
 	__u8	session_id_upper:2,
 		t:1,
 		en:2,
 		cos:3;
 	__u8	session_id:8;
 #elif defined(__BIG_ENDIAN_BITFIELD)
 	__u8	ver: 4,
 		vlan_upper:4;
 	__u8	vlan:8;
 	__u8	cos:3,
 		en:2,
 		t:1,
 		session_id_upper:2;
 	__u8	session_id:8;
 #else
 #error "Please fix <asm/byteorder.h>"
 #endif
 };

 static inline void set_session_id(struct erspan_base_hdr *ershdr, u16 id)
 {
 	ershdr->session_id = id & 0xff;
 	ershdr->session_id_upper = (id >> 8) & 0x3;
 }

 static inline u16 get_session_id(const struct erspan_base_hdr *ershdr)
 {
 	return (ershdr->session_id_upper << 8) + ershdr->session_id;
 }

 static inline void set_vlan(struct erspan_base_hdr *ershdr, u16 vlan)
 {
 	ershdr->vlan = vlan & 0xff;
 	ershdr->vlan_upper = (vlan >> 8) & 0xf;
 }

 static inline u16 get_vlan(const struct erspan_base_hdr *ershdr)
 {
 	return (ershdr->vlan_upper << 8) + ershdr->vlan;
 }

 static inline void set_hwid(struct erspan_md2 *md2, u8 hwid)
 {
 	md2->hwid = hwid & 0xf;
 	md2->hwid_upper = (hwid >> 4) & 0x3;
 }

 static inline u8 get_hwid(const struct erspan_md2 *md2)
 {
 	return (md2->hwid_upper << 4) + md2->hwid;
 }

 static inline int erspan_hdr_len(int version)
 {
 	if (version == 0)
 		return 0;

 	return sizeof(struct erspan_base_hdr) +
 	       (version == 1 ? ERSPAN_V1_MDSIZE : ERSPAN_V2_MDSIZE);
 }

 static inline u8 tos_to_cos(u8 tos)
 {
 	u8 dscp, cos;

 	dscp = tos >> 2;
 	cos = dscp >> 3;
 	return cos;
 }

 static inline void erspan_build_header(struct sk_buff *skb,
 				u32 id, u32 index,
 				bool truncate, bool is_ipv4)
 {
 	struct ethhdr *eth = (struct ethhdr *)skb->data;
 	enum erspan_encap_type enc_type;
 	struct erspan_base_hdr *ershdr;
 	struct qtag_prefix {
 		__be16 eth_type;
 		__be16 tci;
 	} *qp;
 	u16 vlan_tci = 0;
 	u8 tos;
 	__be32 *idx;

 	tos = is_ipv4 ? ip_hdr(skb)->tos :
 			(ipv6_hdr(skb)->priority << 4) +
 			(ipv6_hdr(skb)->flow_lbl[0] >> 4);

 	enc_type = ERSPAN_ENCAP_NOVLAN;

 	/* If mirrored packet has vlan tag, extract tci and
 	 *  perserve vlan header in the mirrored frame.
 	 */
 	if (eth->h_proto == htons(ETH_P_8021Q)) {
 		qp = (struct qtag_prefix *)(skb->data + 2 * ETH_ALEN);
 		vlan_tci = ntohs(qp->tci);
 		enc_type = ERSPAN_ENCAP_INFRAME;
 	}

 	skb_push(skb, sizeof(*ershdr) + ERSPAN_V1_MDSIZE);
 	ershdr = (struct erspan_base_hdr *)skb->data;
 	memset(ershdr, 0, sizeof(*ershdr) + ERSPAN_V1_MDSIZE);

 	/* Build base header */
 	ershdr->ver = ERSPAN_VERSION;
 	ershdr->cos = tos_to_cos(tos);
 	ershdr->en = enc_type;
 	ershdr->t = truncate;
 	set_vlan(ershdr, vlan_tci);
 	set_session_id(ershdr, id);

 	/* Build metadata */
 	idx = (__be32 *)(ershdr + 1);
 	*idx = htonl(index & INDEX_MASK);
 }

 /* ERSPAN GRA: timestamp granularity
  *   00b --> granularity = 100 microseconds
  *   01b --> granularity = 100 nanoseconds
  *   10b --> granularity = IEEE 1588
  * Here we only support 100 microseconds.
  */
 static inline __be32 erspan_get_timestamp(void)
 {
 	u64 h_usecs;
 	ktime_t kt;

 	kt = ktime_get_real();
 	h_usecs = ktime_divns(kt, 100 * NSEC_PER_USEC);

 	/* ERSPAN base header only has 32-bit,
 	 * so it wraps around 4 days.
 	 */
 	return htonl((u32)h_usecs);
 }

 /* ERSPAN BSO (Bad/Short/Oversized), see RFC1757
  *   00b --> Good frame with no error, or unknown integrity
  *   01b --> Payload is a Short Frame
  *   10b --> Payload is an Oversized Frame
  *   11b --> Payload is a Bad Frame with CRC or Alignment Error
  */
 enum erspan_bso {
 	BSO_NOERROR = 0x0,
 	BSO_SHORT = 0x1,
 	BSO_OVERSIZED = 0x2,
 	BSO_BAD = 0x3,
 };

 static inline u8 erspan_detect_bso(struct sk_buff *skb)
 {
 	/* BSO_BAD is not handled because the frame CRC
 	 * or alignment error information is in FCS.
 	 */
 	if (skb->len < ETH_ZLEN)
 		return BSO_SHORT;

 	if (skb->len > ETH_FRAME_LEN)
 		return BSO_OVERSIZED;

 	return BSO_NOERROR;
 }

 static inline void erspan_build_header_v2(struct sk_buff *skb,
 					  u32 id, u8 direction, u16 hwid,
 					  bool truncate, bool is_ipv4)
 {
 	struct ethhdr *eth = (struct ethhdr *)skb->data;
 	struct erspan_base_hdr *ershdr;
 	struct erspan_md2 *md2;
 	struct qtag_prefix {
 		__be16 eth_type;
 		__be16 tci;
 	} *qp;
 	u16 vlan_tci = 0;
 	u8 gra = 0; /* 100 usec */
 	u8 bso = 0; /* Bad/Short/Oversized */
 	u8 sgt = 0;
 	u8 tos;

 	tos = is_ipv4 ? ip_hdr(skb)->tos :
 			(ipv6_hdr(skb)->priority << 4) +
 			(ipv6_hdr(skb)->flow_lbl[0] >> 4);

 	/* Unlike v1, v2 does not have En field,
 	 * so only extract vlan tci field.
 	 */
 	if (eth->h_proto == htons(ETH_P_8021Q)) {
 		qp = (struct qtag_prefix *)(skb->data + 2 * ETH_ALEN);
 		vlan_tci = ntohs(qp->tci);
 	}

 	bso = erspan_detect_bso(skb);
 	skb_push(skb, sizeof(*ershdr) + ERSPAN_V2_MDSIZE);
 	ershdr = (struct erspan_base_hdr *)skb->data;
 	memset(ershdr, 0, sizeof(*ershdr) + ERSPAN_V2_MDSIZE);

 	/* Build base header */
 	ershdr->ver = ERSPAN_VERSION2;
 	ershdr->cos = tos_to_cos(tos);
 	ershdr->en = bso;
 	ershdr->t = truncate;
 	set_vlan(ershdr, vlan_tci);
 	set_session_id(ershdr, id);

 	/* Build metadata */
 	md2 = (struct erspan_md2 *)(ershdr + 1);
 	md2->timestamp = erspan_get_timestamp();
 	md2->sgt = htons(sgt);
 	md2->p = 1;
 	md2->ft = 0;
 	md2->dir = direction;
 	md2->gra = gra;
 	md2->o = 0;
 	set_hwid(md2, hwid);
 }

 #endif
	#ifndef __LINUX_ERSPAN_H
	#define __LINUX_ERSPAN_H

	/*
	* GRE header for ERSPAN type I encapsulation (4 octets [34:37])
	* 0 1 2 3
	* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \|0\|0\|0\|0\|0\|00000\|000000000\|00000\| Protocol Type for ERSPAN \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	*
	* The Type I ERSPAN frame format is based on the barebones IP + GRE
	* encapsulation (as described above) on top of the raw mirrored frame.
	* There is no extra ERSPAN header.
	*
	*
	* GRE header for ERSPAN type II and II encapsulation (8 octets [34:41])
	* 0 1 2 3
	* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \|0\|0\|0\|1\|0\|00000\|000000000\|00000\| Protocol Type for ERSPAN \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Sequence Number (increments per packet per session) \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	*
	* Note that in the above GRE header [RFC1701] out of the C, R, K, S,
	* s, Recur, Flags, Version fields only S (bit 03) is set to 1. The
	* other fields are set to zero, so only a sequence number follows.
	*
	* ERSPAN Version 1 (Type II) header (8 octets [42:49])
	* 0 1 2 3
	* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Ver \| VLAN \| COS \| En\|T\| Session ID \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Reserved \| Index \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	*
	*
	* ERSPAN Version 2 (Type III) header (12 octets [42:49])
	* 0 1 2 3
	* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Ver \| VLAN \| COS \|BSO\|T\| Session ID \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Timestamp \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| SGT \|P\| FT \| Hw ID \|D\|Gra\|O\|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	*
	* Platform Specific SubHeader (8 octets, optional)
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Platf ID \| Platform Specific Info \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* \| Platform Specific Info \|
	* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	*
	* GRE proto ERSPAN type I/II = 0x88BE, type III = 0x22EB
	*/

	#include <linux/ip.h>
	#include <linux/ipv6.h>
	#include <linux/skbuff.h>
	#include <uapi/linux/erspan.h>

	#define ERSPAN_VERSION 0x1 /* ERSPAN type II */
	#define VER_MASK 0xf000
	#define VLAN_MASK 0x0fff
	#define COS_MASK 0xe000
	#define EN_MASK 0x1800
	#define T_MASK 0x0400
	#define ID_MASK 0x03ff
	#define INDEX_MASK 0xfffff

	#define ERSPAN_VERSION2 0x2 /* ERSPAN type III*/
	#define BSO_MASK EN_MASK
	#define SGT_MASK 0xffff0000
	#define P_MASK 0x8000
	#define FT_MASK 0x7c00
	#define HWID_MASK 0x03f0
	#define DIR_MASK 0x0008
	#define GRA_MASK 0x0006
	#define O_MASK 0x0001

	#define HWID_OFFSET 4
	#define DIR_OFFSET 3

	enum erspan_encap_type {
	ERSPAN_ENCAP_NOVLAN = 0x0, /* originally without VLAN tag */
	ERSPAN_ENCAP_ISL = 0x1, /* originally ISL encapsulated */
	ERSPAN_ENCAP_8021Q = 0x2, /* originally 802.1Q encapsulated */
	ERSPAN_ENCAP_INFRAME = 0x3, /* VLAN tag perserved in frame */
	};

	#define ERSPAN_V1_MDSIZE 4
	#define ERSPAN_V2_MDSIZE 8

	struct erspan_base_hdr {
	#if defined(__LITTLE_ENDIAN_BITFIELD)
	__u8 vlan_upper:4,
	ver:4;
	__u8 vlan:8;
	__u8 session_id_upper:2,
	t:1,
	en:2,
	cos:3;
	__u8 session_id:8;
	#elif defined(__BIG_ENDIAN_BITFIELD)
	__u8 ver: 4,
	vlan_upper:4;
	__u8 vlan:8;
	__u8 cos:3,
	en:2,
	t:1,
	session_id_upper:2;
	__u8 session_id:8;
	#else
	#error "Please fix <asm/byteorder.h>"
	#endif
	};

	static inline void set_session_id(struct erspan_base_hdr *ershdr, u16 id)
	{
	ershdr->session_id = id & 0xff;
	ershdr->session_id_upper = (id >> 8) & 0x3;
	}

	static inline u16 get_session_id(const struct erspan_base_hdr *ershdr)
	{
	return (ershdr->session_id_upper << 8) + ershdr->session_id;
	}

	static inline void set_vlan(struct erspan_base_hdr *ershdr, u16 vlan)
	{
	ershdr->vlan = vlan & 0xff;
	ershdr->vlan_upper = (vlan >> 8) & 0xf;
	}

	static inline u16 get_vlan(const struct erspan_base_hdr *ershdr)
	{
	return (ershdr->vlan_upper << 8) + ershdr->vlan;
	}

	static inline void set_hwid(struct erspan_md2 *md2, u8 hwid)
	{
	md2->hwid = hwid & 0xf;
	md2->hwid_upper = (hwid >> 4) & 0x3;
	}

	static inline u8 get_hwid(const struct erspan_md2 *md2)
	{
	return (md2->hwid_upper << 4) + md2->hwid;
	}

	static inline int erspan_hdr_len(int version)
	{
	if (version == 0)
	return 0;

	return sizeof(struct erspan_base_hdr) +
	(version == 1 ? ERSPAN_V1_MDSIZE : ERSPAN_V2_MDSIZE);
	}

	static inline u8 tos_to_cos(u8 tos)
	{
	u8 dscp, cos;

	dscp = tos >> 2;
	cos = dscp >> 3;
	return cos;
	}

	static inline void erspan_build_header(struct sk_buff *skb,
	u32 id, u32 index,
	bool truncate, bool is_ipv4)
	{
	struct ethhdr eth = (struct ethhdr )skb->data;
	enum erspan_encap_type enc_type;
	struct erspan_base_hdr *ershdr;
	struct qtag_prefix {
	__be16 eth_type;
	__be16 tci;
	} *qp;
	u16 vlan_tci = 0;
	u8 tos;
	__be32 *idx;

	tos = is_ipv4 ? ip_hdr(skb)->tos :
	(ipv6_hdr(skb)->priority << 4) +
	(ipv6_hdr(skb)->flow_lbl[0] >> 4);

	enc_type = ERSPAN_ENCAP_NOVLAN;

	/* If mirrored packet has vlan tag, extract tci and
	* perserve vlan header in the mirrored frame.
	*/
	if (eth->h_proto == htons(ETH_P_8021Q)) {
	qp = (struct qtag_prefix )(skb->data + 2 ETH_ALEN);
	vlan_tci = ntohs(qp->tci);
	enc_type = ERSPAN_ENCAP_INFRAME;
	}

	skb_push(skb, sizeof(*ershdr) + ERSPAN_V1_MDSIZE);
	ershdr = (struct erspan_base_hdr *)skb->data;
	memset(ershdr, 0, sizeof(*ershdr) + ERSPAN_V1_MDSIZE);

	/* Build base header */
	ershdr->ver = ERSPAN_VERSION;
	ershdr->cos = tos_to_cos(tos);
	ershdr->en = enc_type;
	ershdr->t = truncate;
	set_vlan(ershdr, vlan_tci);
	set_session_id(ershdr, id);

	/* Build metadata */
	idx = (__be32 *)(ershdr + 1);
	*idx = htonl(index & INDEX_MASK);
	}

	/* ERSPAN GRA: timestamp granularity
	* 00b --> granularity = 100 microseconds
	* 01b --> granularity = 100 nanoseconds
	* 10b --> granularity = IEEE 1588
	* Here we only support 100 microseconds.
	*/
	static inline __be32 erspan_get_timestamp(void)
	{
	u64 h_usecs;
	ktime_t kt;

	kt = ktime_get_real();
	h_usecs = ktime_divns(kt, 100 * NSEC_PER_USEC);

	/* ERSPAN base header only has 32-bit,
	* so it wraps around 4 days.
	*/
	return htonl((u32)h_usecs);
	}

	/* ERSPAN BSO (Bad/Short/Oversized), see RFC1757
	* 00b --> Good frame with no error, or unknown integrity
	* 01b --> Payload is a Short Frame
	* 10b --> Payload is an Oversized Frame
	* 11b --> Payload is a Bad Frame with CRC or Alignment Error
	*/
	enum erspan_bso {
	BSO_NOERROR = 0x0,
	BSO_SHORT = 0x1,
	BSO_OVERSIZED = 0x2,
	BSO_BAD = 0x3,
	};

	static inline u8 erspan_detect_bso(struct sk_buff *skb)
	{
	/* BSO_BAD is not handled because the frame CRC
	* or alignment error information is in FCS.
	*/
	if (skb->len < ETH_ZLEN)
	return BSO_SHORT;

	if (skb->len > ETH_FRAME_LEN)
	return BSO_OVERSIZED;

	return BSO_NOERROR;
	}

	static inline void erspan_build_header_v2(struct sk_buff *skb,
	u32 id, u8 direction, u16 hwid,
	bool truncate, bool is_ipv4)
	{
	struct ethhdr eth = (struct ethhdr )skb->data;
	struct erspan_base_hdr *ershdr;
	struct erspan_md2 *md2;
	struct qtag_prefix {
	__be16 eth_type;
	__be16 tci;
	} *qp;
	u16 vlan_tci = 0;
	u8 gra = 0; /* 100 usec */
	u8 bso = 0; /* Bad/Short/Oversized */
	u8 sgt = 0;
	u8 tos;

	tos = is_ipv4 ? ip_hdr(skb)->tos :
	(ipv6_hdr(skb)->priority << 4) +
	(ipv6_hdr(skb)->flow_lbl[0] >> 4);

	/* Unlike v1, v2 does not have En field,
	* so only extract vlan tci field.
	*/
	if (eth->h_proto == htons(ETH_P_8021Q)) {
	qp = (struct qtag_prefix )(skb->data + 2 ETH_ALEN);
	vlan_tci = ntohs(qp->tci);
	}

	bso = erspan_detect_bso(skb);
	skb_push(skb, sizeof(*ershdr) + ERSPAN_V2_MDSIZE);
	ershdr = (struct erspan_base_hdr *)skb->data;
	memset(ershdr, 0, sizeof(*ershdr) + ERSPAN_V2_MDSIZE);

	/* Build base header */
	ershdr->ver = ERSPAN_VERSION2;
	ershdr->cos = tos_to_cos(tos);
	ershdr->en = bso;
	ershdr->t = truncate;
	set_vlan(ershdr, vlan_tci);
	set_session_id(ershdr, id);

	/* Build metadata */
	md2 = (struct erspan_md2 *)(ershdr + 1);
	md2->timestamp = erspan_get_timestamp();
	md2->sgt = htons(sgt);
	md2->p = 1;
	md2->ft = 0;
	md2->dir = direction;
	md2->gra = gra;
	md2->o = 0;
	set_hwid(md2, hwid);
	}

	#endif